Our group is a little cranky. The brouhaha in the treetops woke us promptly at 5am. This was no dawn chorus, it was an open audition for avian X-Factor. Now, bleary eyed, we stand at the Quinkan reserve in Jowalbinna, facing a rocky escarpment covered in 2,000-year old drawings. Our guide, Ossi, talks us through them and the mysterious shapes of the Aboriginal rock art suddenly come alive with "timaras" (good spirits) and "imjims", floppy-eared mischief-makers, plus spiky catfish and speckled wallabies. Further along the sandstone bluff, deep in Australia's cattle country, we discover every ridge is decorated with ochre paintings, remarkably preserved over centuries.

I'm on a two-week remote Queensland tour taking in the culture of the indigenous people and exploring the side of Australia often overlooked by visitors whizzing up the Sunshine Coast. What's different about this trip is that it also includes a few days' volunteering at a turtle conservation project. "We wanted to give people a taster of volunteering when they no longer have a gap year to spare", says Christopher Hill, the founder of Hands Up Holidays. "We've seen an increasing demand for holidays that combine both sight-seeing and the chance to give something back."

It seems many of us are now looking for more rewarding experiences on our travels and, clearly aware of the environmental impact of flying across the world, are turning to companies like Hands Up Holidays, which also offers sustainable accommodation, employs local guides and returns 10% of profits to the volunteering projects they support. For me, another draw is the chance to get close to one of Australia's most extraordinary, rare and endangered creatures – the marine turtle.

For now we cool off from the sticky afternoon with a beer and a dip in the tea-coloured creek. Dozens of skittish wallabies have emerged through the gum trees. At night in our semi open-air bush cabins, you can hear bat wings flapping as though hundreds of boomerangs have been hurled simultaneously into the moonlight. It's like sleeping in an aviary with the birds on the outside.

We picnic by the Bloomfield river with the Walker sisters, Aboriginal elders from the Kuku Yalanji tribe - the original custodians of the region. Kathleen tells us about plants to henna your hair and why green ants cure a hangover. Her cultural tours were set up in a community with limited employment and a new generation less interested in its heritage. It is the kind of insight you won't find at the more commercially established Tjapukai cultural centre in Cairns, which explores 70,000 years of Aboriginal history through didgeridoo and dance performances.

In the past few days, I have learned more about Australia and its history than on two previous visits and I'm looking forward to seeing yet another side of Queensland at our next stop - the Cape York Turtle Rescue. The conservation project, which is run by the Aboriginal community of Mapoon, is two hours by propeller plane, coast to coast across Australia's most northerly tip – home to the highest concentration of salt-water crocs ("salties") in Australia. This explains why the camp's intimate collection of raised cabins is fenced in. After the dusty 90-minute drive from Weipa, a dip in the shimmering water is clearly out of the question.

No matter, for our task here is to help measure and tag the area's endangered marine turtles. As dusk sets in, we take off in the 4x4 across 24km of silent beach. Our Aboriginal rangers, Lawry and Cecil, and two fellow volunteers, keep their eyes peeled for turtle tracks amid the discarded nets, bottles and plastic that wash up daily on the shore. For millions of years the turtles have navigated predators to lay their eggs on the same beach where they first emerged, only to get tangled up in man's flotsam. You can't help admiring their perseverance as these ancient creatures meticulously scoop out their nests to lay a clutch of ping-pong sized eggs.

The next morning, before the searing heat arrives, we return for the weaklings. My fellow volunteer, Sandy, has become a bit of an expert at digging out the trapped hatchlings from the 60cm-deep nest chambers to carry them to the water.

The experience of seeing these animals in the wild is undeniably moving but I can't help feeling a little useless: with more time I would have liked to help clean up the beach debris. This, I am told, is a fruitless exercise as there is still no barge to transport the volumes of rubbish collected by volunteers and schoolchildren throughout the year. The rangers can only hope the tide won't wash all their good work back into the sea.

Voluntourism has come under scrutiny in recent months. There is no doubt that the income generated by visitors at a fledgling initiative like Mapoon's turtle camp is helping the project and the local community. But are volunteers a help or a hindrance? At the Australian Rainforest Foundation in the Daintree, the world's oldest rainforest, we stop to plant trees as part of a rehabilitation project. A rather nervous-looking guide hands out saplings. These are enthusiastically "planted" into pre-dug holes, only to be trampled on in the rush to get photographs.

We find out exactly how resilient the rainforest is on a Skyrail ride across the Barron Gorge national park in Cairns, and get acquainted with some of its superpowered flora: the hoya plant which heals its leaves within hours, the "wait-a-while" climbing palm with barbed tendrils, and the stinging tree, an innocuous devil of a plant that can cause up to two years of agony. Once you hear about these special powers, a forest is never quite the same again.

It is all the more special that our next stop is a secluded timber treehouse deep in the rainforest at Rose Gums Wilderness Retreat, 80 minutes outside Cairns. The family-run retreat lies in 230 acres of private forest in the highlands of northern Queensland. Jon and Peta Nott, tell us how they set about reforesting the property with 20,000 native species and building nine luxurious carbon-neutral treehouses. In fact, the retreat not only offsets its carbon emissions, it's now 325 tonnes in credit and the next 1,000 trees have just arrived.

Over our two-night stay we build up a picture of how indigenous tribes lived in this tropical landscape, moving from the lowlands to the highlands according to season and harnessing the plants of the rainforest for food and medicine. Back in Cairns our guide, Brad, gives us our final, more literal taste of Aboriginal "bush tucker". Before I know it he has plucked a green ant and dipped its citrus secretion on my tongue. "Was this used for medicine?" I ask him. "Naah, but you just can't leave Australia without licking a green ant's butt", he grins.

Getting there

Hands Up Holidays (0800 783 3554) offer two trips that include the turtle rescue volunteer project: